1. Field of the Invention
The present invention relates to a welding apparatus and a method thereof for a hermetic compressor, and in particular to a welding apparatus and a method thereof for a hermetic compressor which are capable of decreasing a welding time and improving a welding quality.
2. Description of the Prior Art
FIG. 1 is a longitudinal sectional view illustrating a general hermetic compressor.
The general hermetic compressor includes a casing 11, a compressing unit 31 placed inside the casing 11 and compressing a refrigerant, and a driving unit 41 installed at the upper portion of the compressing unit 31 and operating the compression unit 31.
The driving unit 41 includes a stator 43 fixed at the inner circumference of the casing 11 and connected to a power source, a rotor 45 installed rotatable inside the stator 43, and a rotation shaft 47 fixed at the center of the stator 43 and transmitting a rotation force of the rotor 45 to the driving unit 41.
The compressing unit 31 includes a cylinder 33 forming a compressing chamber 49 in which the refrigerant is sucked and compressed, and a roller 35 fixed at the rotation shaft 47, placed inside the cylinder 33 so as to be eccentric and compressing the refrigerant while rotating inside the cylinder 33.
The casing 11 has a cylinder shape opened up and down, a suction pipe 13 sucking the refrigerant into the compressing chamber 49 is installed at the lower portion of the casing 11, and an upper cap 17 and a lower cap 15 are respectively combined at the opened upper and lower portions of the casing 11 in order to seal up the casing 11.
A discharge pipe 19 is installed at the upper cap 17 in order to discharge the refrigerant, and a plurality of power terminals 21 are installed at a certain portion of the upper cap 17 in order to supply power to the driving unit 41.
The plurality of power terminals 21 are supported by the upper cap 17 through a terminal supporting member 23 and surrounded by an insulating tube 25 so as to penetrate the terminal supporting member 23. And, the power terminal 21 is electrically connected to the stator 43 inside the casing 11 by a lead wire 27
Herein, the terminal supporting member 23 is made of a metal material, and the insulating tube 25 is made of a glass material for insulation.
In the meantime, the upper cap 17 and the lower cap 15 are permanently combined to the casing 11 by welding in order to prevent leakage of the refrigerant from the compressing unit 31.
In a method and an apparatus for welding the upper cap 17 and the lower cap 15 to the casing 11, a MIG (metal inert gas) welding apparatus or a MAG (metal active gas) welding apparatus generating and welding arc by continuously supplying an electrode wire and using argon (A) gas or argon+helium (He) gas as an inert gas for protecting the arc is used.
FIG. 2 is a front view illustrating an arrangement of a welding torch of a welding apparatus of the conventional hermetic compressor.
In the conventional welding apparatus, a first welding torch 101 and a second welding torch 103 are placed at the circumference region of the casing 11 so as to be corresponded each other in the radius direction about the center of the casing 11 and a driving unit (not shown) rotating the casing 11 or the welding torches 101, 103 in welding.
In the conventional welding apparatus, an upper cap 17 and a lower cap 15 are respectively inserted into the upper and lower portions of the casing 11, the first and the second welding torches 101, 103 are at 180 degrees at the circumference of the casing 11 so as to be faced each other, when the driving unit is operated, the casing 11 or the welding torches 101, 103 is/are rotated, accordingly the electric welding can be performed through the first welding torch 101 and the second welding torch 103.
However, in the above-mentioned conventional welding apparatus, because the welding is performed by the two welding torches, the casing or the welding torch has to rotate in a 180-degrees arc at least, the welding time is increased, accordingly a productivity is lowered.
When a welding apparatus includes not less than three welding torches, heat generated in welding is excessively transmitted to the insulating tube through the upper cap and the insulation supporting member, accordingly crack can be occurred in the insulating tube as the glass material.
In addition, when welding stress occurs by the variation of a current and a voltage applied to each welding torch due to characteristics of the electric welding, because an additional means for coping with the situation is not included, accordingly lots of errors can occur.
In order to solve above-mentioned problems, it is an object of the present invention to provide a welding apparatus and a method thereof for a hermetic compressor which are capable of decreasing shapely a welding time and improving a productivity by installing not less than three welding torches.
In addition, it is another object of the present invention to provide a welding apparatus and a method thereof for a hermetic compressor which are capable of minimizing an error rate by lowering transmittance of heat generated in a welding torch to a power terminal by controlling the welding torch so as to pass the power terminal only one time.
In order to achieve the above-mentioned objects, a welding apparatus for a hermetic compressor includes a plurality of welding torches placed at the circumference of a casing at regular intervals, a driving unit rotating the casing or the welding torches and a control means controlling a current and a voltage applied to the welding torches according to welding conditions and the driving unit.
The hermetic compressor further includes a display unit displaying information about a detection result of the current and the voltage supplied to the welding torch and information about the welding state in real time.
The welding apparatus for the hermetic compressor includes three welding torches respectively placed at 180 degrees at the circumference of the casing 11 in which an upper cap is inserted.
Two of the three welding torches placed at both sides of a power terminal of the upper cap are installed at 60 degrees from the center of the power terminal.
The welding apparatus for the hermetic compressor includes four welding torches placed at 90 degrees at the circumference of the casing.
The driving unit rotates the welding torches or the casing.
The control means includes a power supply unit applying power to each welding torch, a current and voltage detecting unit detecting a current and a voltage applied to each welding torch, a welding condition setting unit setting a welding condition by including an upper limit of the current and the voltage applied to each welding torch, a heat input outputting unit outputting a heat input transmitted to the upper cap with the detecting result of the current and voltage detecting unit, and a control unit controlling the welding torch and the driving unit according to an electric signal of the heat input outputting unit and an electric signal applied from the welding condition wetting unit.
In order to achieve the above-mentioned object, a welding method for a hermetic compressor in accordance with the present invention includes a first step for setting a welding condition according to characteristics of a hermetic compressor and loading a casing having an inserted upper cap to a welding position, a second step for starting a welding by applying power to a welding torch, operating a driving unit and rotating the welding torch or the casing at a fixed speed when the casing is loaded to the welding position, a third step for detecting a current and a voltage applied to the welding torch and outputting a heat input transmitted from the welding torch to the upper cap in accordance with the detected electric signal when the welding is started in the second step, and a fourth step for stopping the loading of the hermetic compressor and cutting off power supply to the driving unit when the heat input transmitted to the upper cap is compared with a preset value and it is judged the former is larger than the latter in the third step.
The welding method for the hermetic compressor further includes displaying cut off of the power supply to the welding torch and the driving unit in an error occurrence.
In the welding method for the hermetic compressor, when the casing is loaded to the welding torch, the two welding torches are respectively placed at 60 degrees from the center of the power terminal installed at the upper cap.